Oil well drilling fluids



l itcd; rate Pater thee 3,049,491 OIL WELL DRILLING FLUIDS James E. Donham, Qrossett, Ark, assignor to Crossett Chemical Company, a Division of The Crossett Company, Crossett, Ark, a corporation of Arkansas No Drawing. Filed Aug. 27, 1959, Ser. No. 836,324 6 Claims. (Cl. 1252-85) This invention relates to drilling fluids useful in the rotary drilling of oil and gas Wells. More particularly, the invention relates to novel drilling muds which are eflective extreme pressure lubricants for the drill bit.

The rotary drilling of oil and gas wells conventionally entails utilization of a drilling fluid or mud circulated through the well bore and about the drilling bit. It is customary continuously to pump the drilling fluid down the drill stem to the drill bit at the bottom of the bore hole. The stream of drilling fluid circulates about the drill bit and moves upwardly through the annular space between the drill stem and the well bore hole to carry the cuttings out of the well.

A substantial portion of the total time consumed during well drilling operations is taken up in the replacement of drill bits. Inasmuch as changing a bit necessitates pulling the entire string of drill stem, substituting a new bit, and rerunning the entire string of drill stem back into the borehole, it is evident that the time consumed in making bit changes increases roughly in proportion to the depth being drilled. As Wells are being drilled to ever increasing depths, the economic losses attendant upon the increasing amount of time lost in making bit changes cannot be ignored. In addition to the loss of time involved in making bit changes, the necessity for making frequent bit changes, particularly when drilling at substantial depths, may create hazards, such as increasing the likelihood of cave-ins, which may arise as a result of stopping the circulation of the drilling fluid during the change of bits.

Obviously, the necessity for making a bit change is dictated by the exhaustion of the useful life of the bit. Although much has been done toward improving drill bits and drilling techniques in order to prolong useful life, in the present state of rotary bit development, the most frequent limiting factor of bit life is failure of the bearings, rather than the cutting teeth.

Thus, perhaps the most important factor tending to shorten the useful life of a drill bit is the lack of adequate lubrication of the bearings. In the past, efforts have been made to afford lubrication for the bearings by incorporating self-contained lubricating unit in the bits. That such efforts have not been entirely successful is borne out by the fact that conventional bits currently in use are not provided with such self-lubricating units. Consequently, conventional bits receive only such lubrication as may be obtained from the drilling fluid being circulated therethrough. Since the bearings of the bit are subjected to high loads, the value of conventional drilling fluids as bit lubricants leaves much to be desired.

Conventional categories or types of drilling fluids include fresh water; fresh water-base muds which comprise a combination of hydratable clay with water; oil-in-water emulsions free of clay which are known as milk emulsions; emulsion muds which comprise a combination of hydratable clay with oil-in-water emulsions; salt water; and salt water muds comprising salt water clay with salt Water or with oil-in-salt water emulsions.

This invention is concerned with fresh water-base muds, and, more particularly, with novel water-base muds which contain as the essential components thereof fresh water, hydratable clay, and as an extreme pressure bit lubricant, a small amount of floating soap.

Extreme pressure lubricant additives heretofore utilized do not effectively disperse in water-base drilling mud compositions, and hence require concomitant utilization of an emulsifying agent effective to maintain a substantial homogeneity of the mud composition. It is, accordingly, a primary object of this invention to provide a novel fresh water-base drilling mud composition eifective to provide extreme pressure lubrication for the drill bit bearings.

It is a more specific object of the invention to provide a water-base drilling mud composition containing a single additive which is effective both as an emulsifier and as an extreme pressure lubricant.

It is a more specific object of the invention to provide a water-base drilling mud composition which affords comparatively greater bit life than compositions known to the prior art.

It is yet another object of the invention to provide a drilling mud composition which occasions less wear of accessory equipment such as pumps, liners, and drill strings, than analogous compositions known in the prior art.

It is yet another object of the invention to provide a water-base drilling composition which aflords effective extreme pressure lubrication to the drill bit and which minimizes water loss.

it is an additional object of the invention to provide a water-base drilling mud composition which effectively increases the bit penetration rate.

It is a further object of this invention to provide waterbase drilling mud compositions which effectively aid in the removal of cuttings from the area being drilled.

In accordance with this invention, there is provided a water-base drilling mud consisting essentially of fresh water, clay, and floating soap, said floating soap being present on a dry basis in a small amount, substantially less than one percent by Weight of said mud effective to impart extreme pressure lubricating properties thereto.

Dyke et al. Patent 2,468,658 discloses a water-base drilling mud composition comprising water, clay and floating soap. In accordance with the teachings of the Dyke patent, floating soap is utilized in an amount corresponding to at least about 1% by Weight of the drilling fluid. There is no recognition in the Dyke patent that floating soap in any concentration is effective as an extreme pressure lubricant for drilling bit bearings in drilling mud compositions. It is accordingly unexpected in view of the teachings of Dy-ke to discover that floating soap in an amount substantially less than one percent by weight of the drilling fluid provides effective extreme pressure lubrication.

Additionally, Fischer et al. Patents 2,655,475 and 2,687,375 are directed to modifying the water loss properties and cake forming properties of water-clay drilling muds utilizing mixtures of natural gums or organic colloid materials with emulsifying agents. Tall oil soaps are exemplified in amounts of 2 and 5.6%. Again, there is no recognition that small amounts of floating soap or tall oil soap will provide effective extreme pressure lubrication.

The term floating soap as employed in this specification refers to the saponaceous byproduct of a neutral or alkaline pulping of cellulosic materials. Upon concentration of the used pulping liquors from such pulping opera tions, floating soap separates on the surface of the liquor and may be recovered. Such a product may be freed of entrained liquors by salting out, centrifuging, or the like. In general, floating soap is synonymous with or equivalent to tall oil soaps. Accordingly, comparable materials contemplated for use in the invention embrace water-soluble soaps produced from tall oil.

Floating soap is preferably utilized in commercial granulated or free-flowing form as described, inter alia, in U.S. Patents 2,854,419 and 2,854,442. Such material is conventionally prepared by the vacuum-drying, drumdrying, or spray-drying of floating soap. Such commercially available floating soap products may be expected to contain from about 1 to about 35 percent and more frequently from about 3 to about percent by weight of water. The proportions of floating soap specified herein relate to a moisture free basis.

The floating soap is utilized in the drilling mud compositions contemplated by this invention in a small amount substantially less than 1% by weight of the mud effective to impart extreme pressure lubricating properties thereto. As is apparent from the ensuing examples, the floating soap additive imparts extreme pressure lubricating characteristics to fresh water-base drilling mud compositions when present in exceedingly small amounts, hence the invention embraces such drilling mud compositions containing floating soap in an amount substantially less than 1% by Weight. The floating soap concentrate is employed according to this invention in amounts from about 0.04 to about 0.25 percent by weight based on the total weight of the mud composition. Amounts of floating soap from 0.07 to about 0.15 percent constitute a preferred range for water-clay drilling muds.

Drilling bit failure may occur either because the bit teeth wear out or because the bearings fail and seizure occurs. It has been found that floating soap in amounts of 0.25 percent will adequately insure in substantially all cases that the bit bearings will outlast the bit teeth and, consequently, will insure that the maximum bit life is attained. Amounts of floating soap substantially less than 0.04 percent, on the other hand, do not generally impart sufficient lubrication to prevent bearing failure before bit teeth failure. Amounts of floating soap ranging from 0.07 to 0.15 percent insure maximum bit life for most drilling conditions which may be encountered.

The fresh water-base drilling muds embraced by the present invention are those which contain hydratable clay as a viscosity modifier and water-loss reducing agent. Bentonites and sub-bentonites are representative of those commonly employed by the art. The constituency of the mud will vary with circumstance, depending upon ground formation and the like. These muds generally contain from about 1 to about and often from about 2 to about 10% clay and clay-type solids.

The clay may be added to the water at ground level or, in certain instances, fresh water may be circulated through the bit to absorb clay from surrounding ground formations thereby achieving a natural mud having satisfactory characteristics.

Additionally calcium treated (lime based" and gyp),

muds fall within the embrace of this invention. Calcium treated mud comprise clay-containing muds in which the clay has been converted from a natural sodium-based material to a calcium-based material by treatment with lime or gypsum. Calcium treated muds include dispersants such as lignosulfonates as disclosed in Barnes Patent 2,491,436. The proportions of clay employed in calcium treated muds correspond generally to those proportions set forth above.

It will be appreciated that the invention contemplates fresh water-base drilling muds containing in addition to water, clay, and the floating soap extreme pressure additive, conventional ingredients known to be useful in drilling mud formulations. Such additives include anti-foam-.

ing agents, weighting agents, viscosity modifiers, agents for reducing fluid loss, water softeners, and the like. Such materials are well known to the art and are contemplated for use in a conventional manner in the drilling muds with which this invention is concerned. Generally the floating soap additive of this invention is the only surface active agent employed in the drilling fluids of this invention.

The drilling mud compositions of the invention are effectively utilized throughout the entire well drilling operation. However, drilling operations may be initiated iwith fresh water or conventional fresh water-base muds because soft formations in the absence of high specific loads on the drill bit at shallow depths may not require extreme pressure lubrication. Therefore, as dictated by the requirements of the drilling in the formation encountered, the water-base mud is converted to the floating soap-containing mud contemplated by the invention. Such conversions readily may be accomplished during circulation of the water-base mud in the well by adding to the mud in the mud pit or elsewhere an appropriate concentration of floating soap.

The extreme pressure lubricating qualities of the drilling mud compositions of the invention are effectively demonstrated by the experiments reported in the ensuing examples:

EXAMPLE I A fresh water bentonite mud was prepared by dispersing 6% of commercial bentonite, sold under the trade name Aquagel, in tap water and permitting the mixture to gel and properly agev The mud was characterized by a pH of 8.8, a density of 1.04 grams per cc. or 8.7 pounds per gallon.

The lubricity or extreme lubricating properties of the resulting mud were determined by a conventional Baroid extreme pressure mud tester. Essentially, the apparatus consists of a smoothly ground steel collar arranged to rotate in contact with a ground steel block while submerged in the fluid under test. The steel block is mounted on a pivoted lever by means of which the pressure against the rotating collar can be adjusted through a crank and screw arrangement. The torque on the pivoted lever which is proportional to the pressure under which the block and collar are in contact is read from a dial on the lever arm. An arnmeter is provided to measure the power input to the motor which drives the collar. Two determinations may be made with the apparatus; i.e., the breakdown point and the pass point.

To determine the breakdown point, the apparatus is run for thirty seconds with the block out of contact with the collar, after which the block is brought to bear against the collar and the torque is [increased uniformly at the rate of 50 inch pounds per ten seconds until a seizure occurs. Seizure can be detected by a change in the sound and by a sudden increase in the power input to the driving motor. When a seizure has occurred, examination of the block and collar reveals rough, scored surfaces. The block and collar are replaced for each test.

The pass point is determined by repeating the test at successively lower 50 inch pound increments of torque starting near the breakdown point until a value is found at which the machine can be run for 5 minutes without an occurrence of a seizure.

The drilling mud composition formulated in accordance with this example performed in the Baroid test apparatus as reflected by the data reported in Table 1.

Table 1 Floating Soap Breakdown Pass lb./bbl. Wt. Baroid Tirnken Baroid Timkcn percent in 1b. lb. in lb. lb.

The data in Table 1 demonstrate that the limit of the testing machine, i.e. 600 pounds breakdown, was reached with a concentration of floating soap additive of only about 0.14 weight percent; and 600 pounds pass was reached with a concentration of only about 0.17 weight percent.

The data reported under the heading of Timken Pounds in Table 1 expresses the results in terms of the corresponding load on a Timken extreme pressure apparatus using the conversion table supplied with the Baroid equipment. Corresponding Timken loads are reported up to 450 inch pounds, the upper limit of the conversion table. As reflected, inter alia, by Tailleur Patent 2,773,- 030, the load-carrying capacities of muds as reflected by the Timken machine also correlate well with actual field tests. It is thus possible to test the field eflicacy of drilling muds in the laboratory. In general, drilling muds which demonstrate a load-carrying capacity on the Timlcen machine of not less than about 30 pounds, demonstrate excellent extreme pressure lubrication in actual field use.

The significance of the above data can be more fully appreciated when it is recognized that fresh water and fresh water-based muds have no extreme pressure lubricating qualities. Even the lowest pressures applied in the testing machine cause seizure.

EXAMPLE II A fresh-Water mud was formulated employing 6% bentonite clay in water. The mud was modified by the addition of 2 pounds per barrel of pine bark extract and exhibited a pH of 12.0.

Table 2 reflects the results of tests conducted as described in Example I.

A fresh-water bentonite mud was prepared by dispersing 6% of commercial bentonite, sold under the trade name Aquagel, in tap water and permitting the mixture to gel and properly age. The mud was characterized by a pH of about 8.8.

Table 3 reflects the results of tests conducted as described in Example I.

Table 3 Floating Soap Breakdown Pass lbJbbl. Wt. Baroid Timken Baroid Timken percent in 1b. lb. in lb. lb.

EXAMPLE IV A natura water-based clay mud resulting from the drilling of a well in Borden County, Texas, was tested and exhibited a Baroid inch pounds pass of 250 and a Timken point pass of 80. The mud contained 4% native solids and 0.5 pound per barrel of floating soap.

Since modifications of the present invention will be apparent to those skilled in the art, it is intended that the present invention be limited only by the scope of the appended claims.

The incorporation of floating soaps as extreme pressure bit lubricants in other types of drilling mud compositions is shown in my copending applications Serial Nos. 836,- 322, 836,323 and 836,325, filed of even date.

I claim:

1. A drilling fluid consisting essentially of fresh water, clay and floating soap, and floating soap being present in amounts of from about 0.04 to about 0.25% by Weight based on the total weight of the drilling fluid suflicient to impart extreme pressure lubricating qualities to the drilling fluid.

2. The drilling fluid composition of claim 1 wherein the floating soap is present in amounts of from about 0.07 to about 0.15% by Weight.

3. A drilling fluid consisting essentially of fresh water; from about 1 to about 30% by weight of clay based on the total weight of the drilling fluid; and from about 0.04 to about 0.25% by weight of floating soap based on the total weight of the drilling fluid, said floating soap being present in amounts suflicient to impart extreme pressure lubricating properties to the drilling fluid.

4. The drilling fluid composition of claim 3 wherein the floating soap is present in amounts of from about 0.07 to about 0.15 by weight.

5. A drilling fluid consisting essentially of fresh water; from about 2 to about 10% by weight of clay based on the total weight of the drilling fluid; and from about 0.04 to about 0.25% by weight of floating soap based on the total weight of the drilling fluid, said floating soap being present in amounts sufiicient to impart extreme pressure lubricating properties to the drilling fluid.

6. The drilling fluid composition of claim 5 wherein the floating soap is present in amounts of from about 0.07 to about 0.15% by weight.

References Cited in the file of this patent UNITED STATES PATENTS 2,468,657 Dyke et a1. Apr. 26, 1949 2,468,658 Dyke et a1. Apr. 26, 1949 2,655,475 Fischer et a1. Oct. 13, 1953 2,687,375 Fischer et a1. Aug. 24, 1954 2,773,030 Tailleur Dec. 4, 1956 OTHER REFERENCES Ellis: Lubricant Testing, published, 1953, by Scientific Publications (Great Britain) Ltd., pages 147 to 150. 

1. A DRILLING FLUID CONSISTING ESSENTIALLY OF FRESH WATER, CLAY AND "FLOATING SOAP," AND "FLOATING SOAPC8 BEING PRESENT IN AMOUNTS OF FROM ABOUT 0.04 TO ABOUT 0.2K% BY WEIGHT BASED ON THE TOTAL WEIGHT OF THE DRILLING FLUID SUFFICIENT TO IMPART EXTREME PRESSURE LUBRICATING QUALITIES TO THE DRILLING FLUID. 